Just some info. I decided to fast this week. Monday evening to Wednesday afternoon (44hrs) then Wednesday evening to Friday afternoon (44hrs). What I ate in between didn’t pass like 1200 cals. That’s bc I have low calorie food in the house and the time window made it that I was full sooner.
If you ate nothing, then no.
If your calorie intake is negative, you will lose wait over time, so the only way to gain weight is the actual weight of the food and drinks you intake.
If for some reason your weight goes up over time, there would most likely be a medical explanation, such as retaining extra water in your body etc.